Study CEA-III (colon carcinoma antigen III, also known as NCA), CSAp (colon specific antigen p), beta HCG, Regan isoenzyme of alkaline phosphatase, and the major blood group antigens. Discriminate between malignant and nonmalignant cells and determine whether immunocytochemical methods can more easily and accurately detect micrometastatic spread in regional nodules. The cellular location of the various detected antigens shall be investigated and it shall be determined whether shifts in tumor cell populations occur with respect to the expression of a particular tumor antigen as a result of therapy of tumor progression/regression. In addition, attempts will be made to determine the relationship of the expression of these tumor antigens to tumor differentiation and clinical outcome, and to correlate the presence or absence of these tumor markers in the tumor with their use as plasma markers of disease activity. Concommitant determinations of the tissue concentration of these markers will be done.